Ultraviolet absorbing glass and articles thereof

ABSTRACT

Disclosed herein are ultraviolet absorbing glasses. The glasses can be strengthened by a chemical tempering process and maintain good mechanical and optical properties while having a reduced thickness compared to conventional glasses. The ultraviolet absorbing glasses can include coloring agents and can be formed into ophthalmic lenses. Methods of making and using the ultraviolet absorbing glasses are also described.

This application claims the benefit of priority under 35 U.S.C. § 119 ofU.S. Provisional Application Ser. No. 62/126,796 filed on Mar. 2, 2015the content of which is relied upon and incorporated herein by referencein its entirety.

BACKGROUND

Numerous UV-protective glass (oxides) and plastic lens compositions havebeen previously described. Often, a trade-off exists between strength ormechanical properties and UV absorbance. For example, plastic lenses arelightweight due to their low densities; they can also be formed thinnerthan most glasses to further reduce weight. They also generally absorbUV radiation better than their glass counterparts. However, glasslenses, while typically heavier and thicker, are more scratch resistantand have better mechanical strength. Both glass and plastic lenses maybe tinted a variety of colors, with the most common being green, gray,and brown.

One strategy for improving UV absorbance of glass lenses involves addinga cuprous or cuprous-cadmium halide crystal phase to non-photochromiccolorless borosilicate glass. UV absorbance is improved in theseglasses; however, the relative proportions of the oxide components insuch compositions must be adjusted to maintain basicity. Thus, the useof alkali metals and alkaline earth metals is limited, which canadversely affect mechanical and optical properties.

An alternative strategy for improving UV absorbance of glass lensesinvolves the addition of silver salts to the glass composition,including a final hydrogen firing step to product a tint. However, thethickness of such glasses must be kept above about 1.8 mm whenfabricated as lenses to insure adequate mechanical strength.

Thinner glass lenses with good mechanical properties have also beenprepared, but are not designed to absorb UV radiation. Instead, they aredesigned to be used as laminates, with at least some of the scratchresistance and mechanical strength imparted by the additional laminatedlayers.

Consequently, there is a need for a thin glass material with the UVabsorption capabilities of plastic and the high mechanical strength ofglass. Ideally, small amounts of coloring agents could be used toproduce a tint in these glasses without affecting optical or mechanicalproperties. The present application addresses this need.

SUMMARY

Disclosed herein are ultraviolet absorbing glasses. The glasses can bestrengthened by a chemical tempering process and maintain goodmechanical and optical properties while having a reduced thicknesscompared to conventional glasses. The ultraviolet absorbing glasses caninclude coloring agents and can be formed into ophthalmic lenses.Methods of making and using the ultraviolet absorbing glasses are alsodescribed.

The advantages of the invention will be set forth in part in thedescription that follows, and in part will be obvious from thedescription, or may be learned by practice of the aspects describedbelow. The advantages described below will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive.

DETAILED DESCRIPTION

The compositions, methods, and articles described herein can beunderstood more readily by reference to the following detaileddescription. It is also to be understood that the terminology usedherein is for the purpose of describing particular aspects only and isnot intended to be limiting.

It must be noted that, as used in the specification and appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to“an alkali metal oxide” includes mixtures of two or more alkali metaloxides.

Throughout the description and claims of this specification, the word“comprise” and other forms of the word, such as “comprising” and“comprises,” mean including but not limited to, and are not intended toexclude, for example, other additives, components, integers, or steps.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not. For example, the phrase “optionally includes a coloring agent”means that a coloring agent can or cannot be included.

As used herein, the term “about” provides flexibility to a numericalrange endpoint by providing that a given value may be “a little above”or “a little below” the endpoint without affecting the desired result.Ranges may be expressed herein from “about” one particular value, and/orto “about” another particular value. When such a range is expressed,another aspect includes from the one particular value and/or to theother particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint and independently of the otherendpoint.

“Admixing” or “admixture” refers to a combination of two or morecomponents together wherein there is no chemical reaction or physicalinteraction. The terms “admixing” and “admixture” can also include thechemical reaction or physical interaction between any of the componentsdescribed herein upon mixing to produce the composition. The componentscan be admixed alone, in water, in another solvent, or in a combinationof solvents. The order in which the various components of the presentglasses can be admixed with one another can vary.

“Scratch resistance” refers to the ability of the surface and interiorof a lens or other glass article to remain smooth (i.e., avoid scratchesor surface damage) when a hard object is dragged across the surface ofthe lens or glass article. In one aspect, the glass compositionsdisclosed herein are scratch resistant.

“Ultraviolet” or “UV” radiation is electromagnetic radiation with highfrequency and low wavelength. In one aspect, UV radiation has awavelength of between about 10 nm and about 400 nm. “UV absorbance,”meanwhile, refers to an article or compound's ability to blocktransmission of (i.e., to “absorb”) UV radiation. In some aspects, saltsand elements and compounds such as CuO, Cl, Br, SnO, Sb₂O₃, and othersexhibit UV absorbance. In a further aspect, salts, elements or compoundssuch as these are added to the present ultraviolet absorbing glasscompositions to provide the glasses and articles made from the glasseswith UV absorbance properties. In a still further aspect, it isdesirable to produce glass compositions and articles with UV absorbanceto protect, for example, the eyes from UV radiation.

“AS 1067:2003” is a standard for sunglasses and fashion spectaclescreated by Standards Australia/Standards New Zealand Committee CS-053for the purpose of categorizing non-prescription lenses based on glarereduction and UV protection. A category 2 glass according to thisstandard would provide a medium level of glare reduction and good UVprotection. A category 3 glass according to this standard would stillprovide good UV protection, as with category 2, but would have higherglare reduction.

Disclosed are materials and components that can be used for, can be usedin conjunction with, can be used in preparation for, or are products ofthe disclosed compositions and methods. These and other materials aredisclosed herein, and it is understood that when combinations, subsets,interactions, groups, etc., of these materials are disclosed, that whilespecific reference of each various individual and collective combinationand permutation of these compounds may not be explicitly disclosed, eachis specifically contemplated and described herein. For example, if analkali metal oxide is disclosed and discussed and a number of differenttransition metal oxides are discussed, each and every combination andpermutation of alkali metal oxide and transition metal oxide that ispossible is specifically contemplated unless specifically indicated tothe contrary. For example, if a class of molecules A, B, and C aredisclosed, as well as a class of molecules D, E, and F, and an exampleof a combination molecule A-D is disclosed, then even if each is notindividually recited, each is individually and collectivelycontemplated. Thus, in this example, each of the combinations A-E, A-F,B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated andshould be considered disclosed from the disclosure of A, B, and C; D, E,and F; and the example combination A-D. Likewise, any subset orcombination of these is also specifically contemplated and disclosed.Thus, for example, the sub-group of A-E, B-F, and C-E is specificallycontemplated and should be considered from the disclosure of A, B, andC; D, E, and F; and the example combination A-D. This concept applies toall aspects of the disclosure including, but not limited to, steps inmethods of making and using the disclosed compositions. Thus, if avariety of additional steps can be performed, it is understood that eachof these additional steps can be performed with any specific embodimentor combination of embodiments of the disclosed methods, and that eachsuch combination is specifically contemplated and should be considereddisclosed.

Certain materials, compounds, compositions, and components disclosedherein can be obtained commercially or readily synthesized usingtechniques generally known to those of skill in the art. For example,the starting materials and reagents used in preparing the disclosedcompounds and compositions are either available from commercialsuppliers or prepared by methods known to those skilled in the art.

In one aspect, an ultraviolet absorbing glass is provided. Theultraviolet absorbing glass includes (a) a base glass composition withat least the following components by the given weight percentages:

SiO₂ 50-60 B₂O₃ 17.5-22.0 Al₂O₃ 6.5-8.0 Li₂O 3.5-5.5 Na₂O 0.5-7.5 K₂O0.5-7.5 ZrO₂ 2.0-7.0 TiO₂   0-2.0and further includes (b) an ultraviolet component comprising (i) copperoxide and (ii) a chloride source, a bromide source, or a combinationthereof. In some aspects, the amount of copper oxide can be from 0.25 to1.5 parts by weight per 100 parts by weight base composition, or can be0.25, 0.5, 0.75, 1.0, 1.25, or 1.5 parts by weight per 100 parts byweight base composition, where any value of the copper oxide can providea lower and upper endpoint of a range. In a further aspect, the sum ofthe chloride from the chloride source, the bromide from the bromidesource, or a combination thereof can be from 0.2 to 4.0 parts by weightper 100 parts by weight base composition. In a still further aspect, thechloride source can be NaCl, KCl, or another bromide salt and thebromide source can be NaBr, KBr, or another bromide salt.

In one aspect, the amount of copper oxide is from 0.5 to 1.0 parts byweight per 100 parts by weight base composition, or is 0.5, 0.6, 0.7,0.8, 0.9, or 1.0 parts by weight per 100 parts by weight basecomposition, where any value of the copper oxide can provide a lower andupper endpoint of a range. In another aspect, the bromide from thebromide source is from 2.0 to 4.0 parts by weight per 100 parts byweight base composition, or is 2.0, 2.33, 2.5, 3.0, 3.5, or 4.0 parts byweight per 100 parts by weight base composition, where any value of thebromide source can provide a lower and upper endpoint of a range.

In a further aspect, the ultraviolet absorbing glass includes a baseglass composition with at least the following components by the givenweight percentages:

SiO₂ 54.0-58.0 B₂O₃ 19.0-21.0 Al₂O₃ 7.0-8.0 Li₂O 4.0-5.0 Na₂O 0.5-1.0K₂O 6.0-7.0 ZrO₂ 4.0-5.0 TiO₂ 0.5-1.5

In still another aspect, the ultraviolet absorbing glass includes a baseglass composition with at least the following components by the givenweight percentages:

SiO₂ 55.0-57.0 B₂O₃ 20.0-21.0 Al₂O₃ 7.0-8.0 Li₂O 4.0-5.0 Na₂O 4.0-5.0K₂O 0.5-1.5 ZrO₂ 4.0-5.0 TiO₂ 0.5-1.5

In one aspect, the ultraviolet absorbing glasses disclosed herein havetransmission values (expressed as % per mm thickness) at 400 nm lowerthan 1%/mm, or lower than 0.75%/mm, or lower than 0.5%/mm, or lower than0.25%/mm, or lower than 0.1%/mm. In another aspect, the ultravioletabsorbing glasses disclosed herein can achieve at least thistransmission value without the use of copper halide precipitation. In astill further aspect, the ultraviolet absorbing glasses disclosed hereindo not include any elemental silver or silver salts in the batchcomposition. In another aspect, transmission values at 400 nm are lowerthan 0.09%, or 0.08%, or 0.07%, or 0.06%, or 0.05%, or 0.025%.

As used herein, “mechanical strength” refers to a property of a glassarticle, specifically a property of the article to resist breakage,cracking, shattering, deformation, etc., when exposed to outsidephysical forces. In one aspect, it is desirable for articles producedfrom the ultraviolet absorbing glasses disclosed herein to have highmechanical strength. In a further aspect, a chemical tempering processcan be used to increase the mechanical strength of the articlesdisclosed herein.

“ROR” or “modulus of rupture strength” as used herein is one measure ofmechanical strength. This property may also be referred to as “flexuralstrength,” “bend strength,” or “fracture strength.” ROR is a property ofa brittle material and refers to the material's ability to resistdeformation when a load is applied.

“DOL” or “depth of compression” (also referred to as “depth of layer”)is a mechanical and/or physical property of chemically strengthenedglass. Most glasses will have some number of surface flaws. A glass witha high DOL is able to resist breakage due to having a thick, compressedouter layer that is deeper than the surface flaws. Glasses with higherDOL values are also more resistant to scratches, abrasions, and impacts.

In one aspect, chemical tempering of the ultraviolet absorbing glassesdisclosed herein results in a mean modulus of ruptures strength (ROR)greater than or equal to 40,000 psi (about 275 MPa) and a mean depth ofcompression (DOL) greater than or equal to 2.5 mil (about 63 μm). In oneaspect, the ROR is greater than or approximately equal to 45,000 psi; or50,000 psi; or 55,000 psi; or 60,000 psi; or 65,000 psi; or 70,000 psi;or 75,000 psi, where any value can provide a lower and upper endpoint ofa range. In another aspect, the DOL is greater than or approximatelyequal to 65 μm, or 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105μm, or 110 μm, where any value can provide a lower and upper endpoint ofa range.

“Chemical tempering” or “chemtempering” of glass is a process wherebythe glass is exposed to a post-production chemical process to impartadded mechanical strength. Chemical tempering is a surface finishingprocess and may be carried out, for example, in a bath containing apotassium salt. In one aspect, during chemical tempering, surface sodiumions in the glass are replaced by potassium ions from the temperingbath. Chemical tempering can also be a two-step process where the glassis first ion-exchanged with a sodium salt to increase surface sodiumconcentration, then ion-exchanged in a bath containing a potassium salt.In one aspect, chemically tempered glass has little optical distortionand can, in some aspects, be cut after tempering. In one aspect, thepresent ultraviolet absorbing glasses are chemically tempered. Temperingputs the outer surfaces of a glass into compression and increases DOLvalues. Chemically-tempered glass is more likely to break into smallgranules or chunks when it does break, rather than splintering intoshards, and is thus less likely to result in injury upon breakage.

In another aspect, the ultraviolet absorbing glasses disclosed hereinhave excellent resistance to impact breakage. In a further aspect, thisresistance is achieved by a chemical tempering process. In one aspect,chemical tempering consists of immersing the formed glasses in a moltensalt bath. In this aspect, the formed glasses may be immersed for 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,23, or 24 hours, where any value can provide a lower and upper endpointof a range. In a further aspect, the molten salt bath can contain KNO₃and NaNO₃. In this aspect, the KNO₃ can be present at 10%, 20%, 30%,40%, 50%, 60%, 70%, or 80% by weight of the molten salt bath and NaNO₃can be present at 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% by weight ofthe molten salt bath, where any value can provide a lower and upperendpoint of a range. In a still further aspect, the temperature of themolten salt bath is 350° C., 375° C., 400° C., 425° C., or 450° C. Inone aspect, the formed glasses are immersed for 16 hours at 400° C. in amolten salt bath consisting of 60% by weight of KNO₃ and 40% by weightof NaNO₃.

In one aspect, the ultraviolet absorbing glass has a mean modulus ofrupture strength greater (ROR) or equal to 40,000 psi (≈275 MPa) andmean depth-of-compression (DOL) greater than or equal to 2.5 mil (≈63μm) after immersion in a molten salt bath.

In one aspect, maintaining a high ratio of lithium oxide over the sum ofother alkali oxides (such as, for example, Na₂O and K₂O) allows forsimultaneously high ROR and DOL values. In one aspect, this ratio isgreater than or equal to 0.8, 0.9, 1, 1.1, 1.2, or 1.3. Without wishingto be bound by theory, a high lithium oxide content enhances potassiumdiffusion during ion exchange processes (such as, for example, chemicaltempering).

In some aspects, coloring agents are added to the glasses disclosedherein, and in other aspects, the glasses are colorless. In one aspect,when coloring agents are added, the coloring agents add sufficient glarereduction to meet the requirements of class 3 sunglasses under the AS1067:2003 standard. In another aspect, the glasses have good opticalproperties.

In a further aspect, the coloring agent comprises NiO, CoO, Fe₂O₃,Cr₂O₃, MnO₂, a rare earth metal oxide, or any combination thereof. Inthis aspect, the amount of NiO can be less than or equal to 2.5, 2.0,1.5, 1.0, 0.5, 0.1, or 0.05 parts by weight per 100 parts by weight basecomposition; the amount of CoO can be less than or equal to 2.5, 2.0,1.5, 1.0, 0.5, or 0.1 parts by weight per 100 parts by weight basecomposition; the amount of Fe₂O₃ can be less than or equal to 6.0, 5.0,4.0, 3.0, 2.0, 1.5, 1.0, 0.5, or 0.1 parts by weight per 100 parts byweight base composition; the amount of Cr₂O₃ can be less than or equalto 2.0, 1.5, 1.0, 0.5, 0.1, or 0.05 parts by weight per 100 parts byweight base composition; the amount of MnO₂ can be less than or equal to4.0, 3.0, 2.0, 1.5, 1.0, 0.5, or 0.1 parts by weight per 100 parts byweight base composition; and the amount of the rare earth metal oxidecan be less than or equal to 6.0, 5.0, 4.0, 3.0, 2.0, 1.5, 1.0, 0.5,0.1, or 0.05 parts by weight per 100 parts by weight base composition.

In some aspects, the ultraviolet absorbing glass compositions disclosedherein can be formed into an article. In one aspect, that article is anophthalmic lens. In a further aspect, the ophthalmic lenses disclosedherein can be used in sunglasses. In yet another aspect, the ultravioletabsorbing glasses disclosed herein can have a thickness of less than orequal to about 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7mm, 1.8 mm, 1.9 mm, or 2.0 mm, where any value can provide a lower andupper endpoint of a range. In one aspect, the ultraviolet absorbingglass is a sunglass lens and has a thickness of 1.4 mm. In one aspect,the ultraviolet absorbing glass can be laminated or coated with aprotective layer. In a further aspect, the ultraviolet absorbing glasscan achieve the desired thickness and maintain good mechanical strengthwithout the inclusion of any laminating or protective layers.

Examples

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thecompositions and methods described and claimed herein are made andevaluated, and are intended to be purely exemplary and are not intendedto limit the scope of what the inventors regard as their invention.Efforts have been made to ensure accuracy with respect to numbers (e.g.,amounts, temperature, etc.), but some errors and deviations should beaccounted for. Unless indicated otherwise, parts are parts by weight,temperature is in ° C. or is at ambient temperature, and pressure is ator near atmospheric. Numerous variations and combinations of reactionconditions (e.g., component concentrations, desired solvents, solventmixtures, temperatures, pressures, and other reaction ranges andconditions) can be used to optimize the product purity and yieldobtained from the described process. Only reasonable and routineexperimentation will be required to optimize such process conditions.

Glass Composition Ranges

The present glasses can be prepared using conventional meltingtechniques and can be molded into any desired shape using conventionalglass forming techniques. Following formation, the ultraviolet absorbingglasses are heat-treated at a temperature between 550° C. and 650° C.for a period ranging from 5 minutes to 2 hours to induce copperprecipitation, which improves absorption of UV light.

Exemplary ranges for the various components of the present ultravioletabsorbing glasses are provided below. Particular components and amountswere determined based on practical glass-making considerations as wellas their effects on physical, mechanical, and/or optical properties ofthe resulting glasses. The amounts of base glass components are providedin Table 1, where the sum of the components equals 100%.

TABLE 1 Base Glass Composition Oxide Weight % SiO₂ 50-60 Al₂O₃ 17.5-22  B₂O₃ 6.5-8   ZrO₂ 3.5-5.5 Li₂O 0.5-7.5 Na₂O 0.5-7.5 K₂O 2-7 TiO₂ 0-2

Further to the ranges given in Table 1, when the base glass compositionis expressed in cationic %, Li₂O/(Na₂O+K₂O)≥1.0.

The ultraviolet absorbing component used in the glass compositions inthe examples are provided in Table 2.

TABLE 2 Components Generating UV Absorption Oxide Weight % CuO 0.25-1.5 Cl 0-3 Br 0-3 Cl + Br 0.2-4   SnO 0-4 Sb₂O₃ 0-4

For tinted glass compositions, the components provided in Table 3 andamounts thereof can be used.

TABLE 3 Coloring Agents Oxide Weight % NiO 0-2.5 CoO 0-2.5 Fe₂O₃ 0-6  Cr₂O₃ 0-2   MnO₂ 0-4   Others, including Er₂O₃, 0-5   Pr₂O₃, and relatedoxides

Impact of Thickness Reduction on Commercial Glass

Tests were performed on a commercially available glass (CORNING® 82515,also known as GX15) to demonstrate that a reduction in thickness of anyglass leads to an increase in transmission T at 400 nm, an increase intransmission in the visible range (seen in change in Tv (IIItC 2°) driftin color (seen in change in chromatic coordinates x and y), and a lossof UV absorption. Results are presented in Table 4.

TABLE 4 Impact of Reduction in Thickness on Glass Properties 1 2 3 4Center thickness (mm) 1.5 1.8 1.9 2 Tv (IIItC 2°) 19.2 13.4 12.1 11.0 x0.3162 0.3161 0.3167 0.3181 y 0.3483 0.3540 0.3563 0.3595 Class (AS1067:2003) 2 3 3 3 T (400 nm) in % 8.4 4.8 4.1 3.5

Compositions and Optical Properties of Example Glasses

Various glasses were constructed having concentrations of components asdescribed in Tables 1-3 and their optical properties were tested.Results are presented in Table 5. Typical values for a commercial graysunglass material (GX15) appear in column 5. For most glasses, basecomposition was held constant and UV-absorbing elements and/or coloringagents were varied. Variations of coloring agents resulting in a grayglass are illustrated in columns 6-9 of Table 5.

TABLE 5 Compositions and Optical Properties of Various Glasses 5 6 7 8 910 11 12 Oxide (Weight % Batched) SiO₂ 53.7 53.1 53.0 54.0 52.4 51.652.3 B₂O₃ 19.3 19.0 19.0 19.4 18.8 18.5 18.7 Al₂O₃ 7.0 6.9 6.9 7.0 6.96.7 6.8 ZrO₂ 4.3 4.3 4.3 4.4 4.2 4.2 4.2 Li₂O 4.0 4.0 4.0 4.1 3.9 3.93.9 Na₂O 0.8 0.8 0.8 4.0 0.8 0.7 0.7 K₂O 6.1 6.0 6.0 0.9 5.9 5.8 5.9TiO₂ 1.1 1.0 1.0 1.1 1.0 1.0 1.0 UV Absorbing and Coloring Agents CuO0.77 0.77 0.77 0.77 0.77 0.77 0.77 Br 2.33 2.33 2.33 2.33 2.33 2.33 2.33NiO 0 0 0 0 0 0 0.045 CoO 0.118 0.235 0.27 0.27 0 0 0.085 Fe₂O₃ 0.3 1.51.65 1.65 2.5 2.5 2.5 Cr₂O₃ 0.18 0.017 0.025 0.025 0 0 0.045 MnO₂ 0 0 00 0.5 2 0.5 Oxide (Cationic % Batched) Li₂O 13.1 13.1 13.1 13.1 13.113.1 13.1 Na₂O 1.1 1.1 1.1 6.3 1.1 1.1 1.1 K₂O 6.2 6.2 6.2 1.0 6.2 6.26.2 Na₂O + K₂O 7.3 7.3 7.3 7.3 7.3 7.3 7.3 Li₂O/(Na₂O + K₂O) 1.79 1.791.79 1.79 1.79 1.79 1.79 Optical Properties Ctr. Thickness (mm) 2 1.41.4 1.4 1.4 1.4 1.4 1.4 Tv (IIItC 2°) 14.0 35.7 19.9 15.7 17.7 27.2 21.524.6 x 0.3180 0.2759 0.3137 0.3161 0.3151 0.4650 0.5290 0.4618 y 0.35500.3292 0.3445 0.3511 0.3500 0.4535 0.4515 0.4536 Class (AS 1067:2003) 32 2 3 3 2 2 2 T (400 nm) in % 0 0 0 0 0 0 0

Glass 8 demonstrates optical properties at a 1.4 mm center thicknessresembling those of a thicker (2 mm) commercial product (GX15) (see Tv(IIItC 2°) values), though with an improved UV absorption (see T (400nm) values). As seen with glass 9, alkali balance can be changed withouta loss in optical performance of the ultraviolet absorbing glass.However, Li₂O/(Na₂O+K₂O), expressed in cationic percent, should bemaintained at greater than or equal to 1 for mechanical reasons. Glasses10-12 represent brown glasses that can be obtained from the presentformulations based on changes in coloring agents. Other coloring agentsare also contemplated.

Mechanical Properties of Various Glasses

Lenses were prepared from two ultraviolet absorbing glasses as describedabove (columns 8 and 9) and were compared to a colorless UV absorbingcommercially available glass (CORNING® UV Clear 8010, column 13). Theseproperties are provided in Table 6.

TABLE 6 Mechanical Properties of Various Glasses Glass Code 13 (UV Clear8010) 8 9 Oxide (Weight % Batched) SiO₂ 48.5 53.0 54.0 B₂O₃ 20.3 19.019.4 Al₂O₃ 8.6 6.9 7.0 ZrO₂ 3.5 4.3 4.4 Li₂O 2.1 4.0 4.1 Na₂O 3.4 0.84.0 K₂O 5.6 6.0 0.9 BaO 4.7 0 0 TiO₂ 0 1.0 1.1 CuO 0.77 0.77 0.77 Br2.33 2.33 2.33 CoO 0 0.27 0.27 Fe2O3 0 1.65 1.65 Cr2O3 0 0.025 0.025Oxide (Cationic % Batched) Li₂O 7.0 13.1 13.1 Na₂O 5.5 1.1 6.3 K₂O 6.06.2 1.0 Na₂O + K₂O 11.5 7.3 7.3 Li₂O/(Na₂O + K₂O) 0.61 1.79 1.79Mechanical Properties Average ROR (MPa) 309 393 524 Standard Deviation61 72 73 ROR (Psi) 44800 57000 76000 DOL (μm) 61 70 105 DOL (mil) 2.42.8 4.1

Compared to the commercially available product, lithium oxide wasmaintained at a higher level in the present ultraviolet absorbingglasses to enhance potassium diffusion during ion exchange processes.This leads to better mechanical resistance (see average ROR value) whensamples are tested after chemical tempering. These higher ROR valuesare, in the present instance, compatible with thinner lenses. To balancethese properties, a high ratio of lithium oxide to the sum of all otheralkali metal oxides is required. In this case, Li₂O/(Na₂O+K₂O),expressed in cationic percent, was greater than or equal to 1.0.

Throughout this application, various publications are referenced. Thedisclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the compounds, compositions, and methods described herein.

Various modifications and variations can be made to the materials,methods, and articles described herein. Other aspects of the materials,methods, and articles described herein will be apparent fromconsideration of the specification and practice of the materials,methods, and articles disclosed herein. It is intended that thespecification and examples be considered as exemplary.

What is claimed is:
 1. An ultraviolet absorbing glass comprising (a) abase glass composition comprising in weight percent: SiO₂ 50-60 B₂O₃17.5-22.0 Al₂O₃ 6.5-8.0 Li₂O 3.5-5.5 Na₂O 0.5-7.5 K₂O 0.5-7.5 ZrO₂2.0-7.0 TiO₂   0-2.0

and (b) an ultraviolet component comprising (i) copper oxide and (ii) achloride source, a bromide source, or a combination thereof, wherein theamount of copper oxide is from 0.25 to 1.5 parts by weight per 100 partsby weight base composition; and the sum of the chloride derived from thechloride source, the bromide derived from the bromide source, or acombination thereof is from 0.2 to 4.0 parts by weight per 100 parts byweight base composition.
 2. The glass of claim 1, wherein the base glasscomposition comprises in weight percent: SiO₂ 54.0-58.0 B₂O₃ 19.0-21.0Al₂O₃ 7.0-8.0 Li₂O 4.0-5.0 Na₂O 0.5-1.0 K₂O 6.0-7.0 ZrO₂ 4.0-5.0 TiO₂ 0.5-1.5.


3. The glass of claim 1, wherein the base glass composition comprises inweight percent: SiO₂ 55.0-57.0 B₂O₃ 20.0-21.0 Al₂O₃ 7.0-8.0 Li₂O 4.0-5.0Na₂O 4.0-5.0 K₂O 0.5-1.5 ZrO₂ 4.0-5.0 TiO₂  0.5-1.5.


4. The glass of claim 1, wherein the molar ratio of Li₂O to (Na₂O+K₂O),expressed in cationic percent, is greater than or equal to
 1. 5. Theglass of claim 1, wherein the amount of copper oxide is from 0.5 to 1.0parts by weight per 100 parts by weight base composition and the bromidederived from the bromide source is from 2.0 to 4.0 parts by weight per100 parts by weight base composition.
 6. The glass of claim 1, whereinthe chloride source is NaCl or KCl and the bromide source is NaBr orKBr.
 7. The glass of claim 1, wherein the ultraviolet absorbing glassfurther comprises one or more coloring agents.
 8. The glass of claim 7,wherein the coloring agent comprises NiO, CoO, Fe₂O₃, Cr₂O₃, MnO₂, arare earth metal oxide, or any combination thereof.
 9. The glass ofclaim 8, wherein the amount of NiO is less than or equal to 2.5 parts byweight per 100 parts by weight base composition; the amount of CoO isless than or equal to 2.5 parts by weight per 100 parts by weight basecomposition; the amount of Fe₂O₃ is less than or equal to 6.0 parts byweight per 100 parts by weight base composition; the amount of Cr₂O₃ isless than or equal to 2.0 parts by weight per 100 parts by weight basecomposition; the amount of MnO₂ is less than or equal to 4.0 parts byweight per 100 parts by weight base composition; and the amount of therare earth metal oxide is less than or equal to 6.0 parts by weight per100 parts by weight base composition.
 10. The glass of claim 1, whereinthe ultraviolet absorbing glass is prepared from a batch compositionthat does not include elemental silver, a silver salt, or a combinationthereof.
 11. The glass of claim 1, wherein the ultraviolet absorbingglass has a transmission of less than or equal to 1%/mm at 400 nm. 12.The glass of claim 1, wherein the ultraviolet absorbing glass has a meanmodulus of rupture strength greater or equal to 40,000 psi (≈275 MPa)and mean depth-of-compression (DOL) greater than or equal to 2.5 mil(≈63 μm) after immersion in a molten salt bath consisting of 60 wt % ofKNO₃ and 40 wt % of NaNO₃ for 16 hours at 400° C.
 13. A glass articlecomprising the ultraviolet absorbing glass of claim
 1. 14. The articleof claim 13, wherein the article comprises an ophthalmic lens.
 15. Thearticle of claim 14, wherein the ophthalmic lens is a lens forsunglasses.
 16. The article of claim 14, wherein the lens has athickness of 1 mm to less than 2 mm.
 17. The article of claim 14,wherein the lens has a thickness of 1.2 mm to 1.6 mm.